Thermal ink ribbon traction device

ABSTRACT

A traction device has an origin cylinder ( 1 ) of heat-sensitive ink ribbon ( 2 ), a rewinding cylinder ( 5 ), traction means and a marking header. The device prevents unused segments of ribbon being left between markings. The device has a moving support ( 6 ) guiding the ribbon ( 2 ) along an additional path ( 16 ), braking means ( 10, 11, 12, 14 ) for the origin cylinder ( 1 ). When the ribbon ( 2 ) is tractioned and the origin cylinder is braked, the support ( 6 ) is forced to move against the action of an elastic element ( 13 ), reducing the additional path ( 16 ). Thus, after a marking (a-b) the ribbon and the support ( 6 ) move back so that the next marking (b-d) is made immediately after the first marking (a-b). The braking means, after one or more markings, are released, unrolling a length of ribbon ( 2 ) from the origin cylinder, then braking again, with the process repeated.

OBJECT OF THE INVENTION

The invention relates to a traction device for heat-sensitive inkribbons as those used for marking surfaces, of the type which allow tofully employ the heat-sensitive ink ribbon, as currently devices areavailable in which unused ribbon segments are left between one markingand another. For this purpose the invention intends to use thesesegments by rewinding the ribbon using a simple and inexpensive device.

The invention is applicable to any type of marking with heat-sensitiveink ribbons, such as in marking plastic film with barcodes or othertypes of data.

BACKGROUND OF THE INVENTION

There exist in the present state of the art well-known devices fortraction of heat-sensitive ink ribbon which comprise a cylinder oforigin of the heat-sensitive ink ribbon which is guided by small rollersto a rewinding cylinder, which is related to a traction mechanism. Inthe path of the ribbon is provided at least one marking head, so thatbetween markings as the ribbon advances there is a segment of ribbonleft unused.

These type of devices have the disadvantage of wasting a large amount ofheat-sensitive ink ribbon.

To solve this drawback a system is known which allows to rewind theribbon so that marking is allowed using the ribbon segments which runbetween markings, for which means are provided which allow the rewindingcylinder to rotate in the sense opposite the advance sense. These meansinclude two shafts, each related to a motor, which drive the ribbon whenthe rewinding cylinder is turned in said opposite sense, therebyallowing the ribbon to move backwards. This system requires to installadditional motors and a precise electronic control, so that it is asophisticated system with a high cost.

DESCRIPTION OF THE INVENTION

To achieve the aforementioned objectives the invention has developed anovel traction device for heat-sensitive ink ribbon which allows to usethe entire ribbon, by means of a simple and inexpensive device.

With this purpose the device of the invention includes novel means forrewinding and tensioning the ribbon, characterised in that they includea moving support provided with guiding means for the ribbon, so that theribbon executes an additional motion. In addition means are providedwhich brake the cylinder of origin so that when the ribbon is driven inthe forward direction with the origin cylinder braked, the ribbon makesthe support advance against the action of an elastic element whichcomplements said support, thereby reducing the additional path traveledby the ribbon, so that after marking the driving means force a backwardsmotion of the ribbon. This backwards motion implies that the supportmoves back under the action of the elastic element, to place the markinghead in a segment prior to the end of the marking already performed,equivalent to the space traveled by the ribbon during the time taken bythe header to descend when making another mark. Thus, when this new markis made the header will meet the ribbon just after the last markingperformed, so that the entire ribbon is used in the marking.

In this manner the forwards-backwards motion of the ribbon does notaffect in any way the cylinder of origin, which remains braked, thusgreatly simplifying the forwards-backwards motion of the ribbon.

The braking means for the origin cylinder are driven by the movingsupport, so that after performing one or several markings with thecorresponding advances and returns the support will release the brakingmeans, to unroll a length of ribbon as requested by the traction meansin a forward direction.

The braking means of the cylinder of origin acts when the moving supportreaches a set advance position in which in contacts said braking meansand these release the cylinder of origin. Thus while maintaining theadvance of the traction means, the ribbon is unrolled by successivebrakings-releases of the origin cylinder. Afterwards the tractionrotation is inverted making the support return due to the action of thespring, so that the origin cylinder is again locked.

The entire process is repeated successively, and all while maintainingthe ribbon tense by means of the elastic element which aids the movingsupport.

In order to attain this functionality the braking means of the origincylinder are determined by a swivelling lever aided by a spring providedwith a shoe, so that the spring keeps the shoe presses against the shaftof the origin cylinder.

The lever is placed in the path of the support, so that when the supportcontacts with it the lever swivels against the action of the spring,causing the release of the origin cylinder. This situation allowsunwinding of the origin cylinder when the ribbon is tractioned.

The elastic element which complements the support is a spring. Saidsupport is retained in guides in which it slides during its forward andbackward motion.

Additionally, a stop is provided which limits the run of the supportduring its backwards motion, in order to ensure the correct operation ofthe device.

The guide means for the ribbon provided in the support consist of acylinder which aids the advance and return of the ribbon.

These and further characteristics of the invention will be made apparentin view of the accompanying drawings, where for purposes of illustrationonly the following is shown.

BRIEF DECRIPTION OF THE DRAWINGS

FIG. 1 shows an elevation view of an embodiment for the traction devicefor heat sensitive ink ribbon of the invention, in which the origincylinder is represented in a discontinuous line to reveal the entirebraking mechanism of the shaft of said cylinder.

FIGS. 2 to 5 show a schematic representation of the marking processusing the device of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

A description of the invention follows with reference to the figuresdescribed above.

The traction device of the invention comprises a removable frame (17)mounted on a machine with heat sensitive marking devices which requireheat-sensitive ribbon for said marking process.

In removable frame (17) is included an origin cylinder (1) which carriesthe heat-sensitive ink ribbon (2), which is guided by rollers (3) to atraction cylinder (4) which is related by a transmission belt (15) to arewinding cylinder (5).

When the removable frame (17) is mounted on the marking machine itsheads are next to the lower horizontal segment (18) of theheat-sensitive ink ribbon (2) (not shown in the figure as they are anthe object of the invention).

Additionally the removable frame (17) has a moving support (6) retainedby guides (8) and which includes a roller (7) on which is guided theheat-sensitive ink ribbon (2), so that the latter follows an additionalpath (16).

The moving support (6) is complemented by a spring (13) which pulls onit so that the tension of the heat-sensitive ink ribbon (2) is alwaysmaintained.

At the rear end of the run of the moving support (6) is provided a stop(9) which limits its run.

Additionally, a lever (10) is provided which is retained by a shaft (12)and which includes a shoe (11). Lever (10) is complemented by a spring(14), so that said spring keeps the shoe (11) pressed against the shaft(1′) of the origin cylinder (1), and such that an end of lever (10) isplaced at the end of the advance path of the moving support (6).

Thus, to begin with the ribbon is mounted so that the el moving support(6) is in contact with stop (9) so that the origin cylinder (1) isbraked. Marking is performed by placing head (19) on point (a) (FIG. 2)while the cylinder (4) causes the advance of the heat-sensitive inkribbon (2), which pulls on the moving support (6), which overcomes theresistance of the spring (13) and moves along the guides (8), reducingthe additional path (16).

During the advance of the ribbon the marking takes place (a-b) (FIG. 3).Afterwards the rotation of the cylinder (4) is inverted, whilemaintaining the origin cylinder (1) braked so that as the support (13)is pulling on the support (6) the ribbon is forced to return until theheader is placed at point (c). The distance (c-b) corresponds to thedistance advanced by the ribbon in the time required for the header todescend and contact the said ribbon (2).

Therefore, after the header is located on point (c) a new marking takesplace, with the advance of the ribbon and the descent of the header(19), which contacts the ribbon at point (b), exactly where the previousmarking ended, at which point begins the marking (b-d).

This process is repeated to perform successive markings, so that thereare no unused segments of ribbon between markings.

During the process described the moving support (6) runs from theposition where it is in contact with stop (9) until it presses on lever(10), which lever is jointed to shaft (12), causing the release of shaft(1′) of the origin cylinder (1). Thus the ribbon is unrolled in anamount required by the traction. Since the origin cylinder is brakedagain as soon as the moving support (6) stops pressing on the lever(10), to unroll the required length of ribbon the traction must act inthe advance direction, with consecutive brakings-releases of the origincylinder until the required ribbon is unrolled. Said brakings-releasesoccur so quickly that they can hardly be appreciated by the eye. Afterthe required length of ribbon is unrolled the traction rotationdirection is inverted so that the moving support (6) travels backtowards the stop (9) as far as determined by the action of the spring(13), all such that the ribbon tension is maintained. In addition,during this return motion of the support (6) it stops acting on thelever (10), so that by action of the spring (14) the shoe (11) againcontacts the shaft (1′) of the origin cylinder (1), again causing thebraking of said cylinder (1). The several brakings are attained quiteefficiently as the inertia of the cylinder (1) during its unrolling issmall.

It should be remarked that for high marking speeds the cylinder inertiais a significant parameter, as if it acquires a high inertia braking ishindered and thus the precision of the device is reduced.

The above described process is repeated sequentially until exhaustingthe heat-sensitive ink ribbon (2) wound on cylinder (1).

Therefore, the device of the invention allows to fully use the ribbon bymeans of a simple, precise and inexpensive mechanism.

What is claimed is:
 1. Traction device for heat-sensitive ink ribbon,said device comprising: an origin cylinder (1) for the heat-sensitiveink ribbon (2); traction means; a rewinding cylinder (5) which ismechanically associated with said traction means; a plurality of rollers(3) for guiding the ribbon (2) towards said rewinding cylinder; at leastone marking header positioned along a path of the ribbon (2), andadapted to form markings on the ribbon (2) with rising and lowering ofthe header and advance of the ribbon (2); returning and tensioning meansfor returning and tensioning the ribbon (2) and allowing the markings tobe made on said ribbon without unused segments of said ribbons beingleft between the markings, wherein the returning and tensioning meanscomprise an elastic element (13) and a moving support (6) which isprovided with guiding means for guiding the ribbon (2) so that theribbon follows an additional motion (16); and braking means (10, 11, 12,14) for braking the origin cylinder (1) so that as the ribbon (2)advances, the moving support (6) is forced to advance against action ofsaid elastic element (13) which complements said moving support (6),thereby reducing the additional motion (16) of the ribbon (2); whereinafter a first marking (a-b) has been made in a segment of said ribbon,the traction means move the ribbon backwards, together with the support(6) by action of the elastic element (13), to place the segment of saidribbon (a-b) under the header at a point (c) so that when the ribbonagain advances to perform a second marking (b-d), the second marking isperformed just after the first marking (a-b); the braking means areactuated by the moving support so that after a predetermined number ofmarkings are performed, the support releases the braking means,unrolling a required length of said ribbon; and the ribbon (2) ismaintained tense at all times.
 2. Traction device for heat-sensitive inkribbon as claimed in claim 1, wherein the braking means is actuated whenthe moving support (6) reaches a certain advance position where themoving support contacts the braking means; and the braking means, whenactuated, release the origin cylinder (1) so that the traction means, ina forward direction, unwind the ribbon (2) and then return, by theaction of the elastic element (13), from the advance position until thebraking means again brake the origin cylinder (1).
 3. Traction devicefor heat-sensitive ink ribbon as claimed in claim 2, further comprisinga stop (9) which limits the motion of the moving support in a returnpath.
 4. Traction device for heat-sensitive ink ribbon as claimed inclaim 1, wherein the braking means consist of a swiveling lever (10)provided with a shoe (11) and a spring (14) which keeps the shoe (11)pressed against a shaft (1′) of the origin cylinder (1).
 5. Tractiondevice for heat-sensitive ink ribbon as claimed in claim 4, wherein theswiveling lever (10) is placed in a path of the moving support (6), suchthat, when said moving support contacts the lever, the lever swivels,overcoming the action of the spring (14) and separating the shoe (11)from the shaft (1′) of the origin cylinder (1); and when the lever (10)is no longer acted upon by said moving support, the spring (14) againforces the shoe (11) to brake the origin cylinder.
 6. Traction devicefor heat-sensitive ink ribbon as claimed in claim 1, wherein the elasticelement which complements the moving support (6) is a spring (13). 7.Traction device for heat-sensitive ink ribbon as claimed in claim 1,wherein the moving support (6) is slidably retained by guides (8). 8.Traction device for heat-sensitive ink ribbon as claimed in claim 1,wherein the guiding means of the moving support are embodied in a roller(7).